The field of this invention generally is related to chemical production methods employing electro-catalytic reaction mechanisms, and more particularly, to methods and systems using vegetable oil and other non-petroleum oil feedstocks to make synthetic compounds useful as or in a variety of specialty chemical products or other useful materials.
Chemical syntheses are ubiquitous and important to numerous industries throughout the world, particularly the industries involved in the production of organic chemicals, polymers, pharmaceuticals, inorganic chemicals, and specialty chemicals. Due to the time and cost of various chemical synthesis processes, industries are continually striving to reduce processing time and cost, to eliminate or simplify purification/separation steps, to decrease the energy cost of production, to increase overall product yields, and to improve the efficiency of chemical synthesis.
Biodiesel
Fossil fuels, particularly coal, oil, and natural gas, are the primary fuels of industrialized society. However, the supply of fossil fuel is limited and non-renewable, and its use is believed to contribute to substantial environmental pollution and health issues. Thus, there is a tremendous resource and environmental burden to find alternative renewable energy sources to the non-renewable fossil fuel.
A viable alternative to fossil fuel is biodiesel, a renewable source of energy. Biodiesel (or bio-fuel) is the name for a variety of ester-based fuels (e.g., fatty esters) generally made from vegetable oils, such as soybean oil, canola or hemp oil, or sometimes from animal fats through a simple transesterification process.
Biodiesel offers many advantages. Biodiesel runs in any conventional, unmodified diesel engine; thus, no engine modifications are necessary. Biodiesel can be used alone or mixed in any amount with petroleum diesel fuel. For example, a 20% blend of biodiesel with (petroleum-based) diesel fuel is called “B20,” a 5% blend is called “B5.” This fuel can be stored anywhere that petroleum diesel fuel is stored, and all diesel fueling infrastructure including pumps, tanks and transport trucks can use biodiesel without modifications. In addition, biodiesel can provide a net reduction in CO2 emissions and produce no sulfur dioxide when burned.
Conventional biodiesel improves engine emissions in most categories when compared to pipeline petroleum diesel fuel. Blends containing higher concentrations of conventional biodiesel, however, disadvantageously show a proportional increase in emissions of nitrogen oxides (NOX). For instance, it is documented that use of a conventional biodiesel blended with petroleum diesel fuel in an 80% petroleum/20% biodiesel blend increases nitrous oxide emissions by 2 to 11%. Presently, NOX emissions are a significant limitation to the widespread adoption of biodiesel fuels.
Some researchers have sought to address the NOX issue by incorporating certain fuel additives into the biodiesel. For example, U.S. Pat. No. 5,578,090 to Bradin discloses a fuel additive composition including fatty acid alkyl esters and glyceryl ethers. The additive-containing fuel is made by a multi-step process that includes separation of glycerol from biodiesel, conversion of glycerol to glycerol ether, and then addition of the glycerol ether back into the biodiesel fuel. Other researchers describe controlling engine emission NOX by adding water to the fuel, which cools the combustion process and reduces the formation of NOX. However, that process undesirably lowers fuel BTU value by replacing fuel with water. It would be desirable to provide a biodiesel fuel that would lower NOX emissions without lowering fuel BTU value, and to provide simpler and less expensive methods producing such fuels.
Conventional methods of producing biodiesel fuel or fuel additive are based on conventional surfactant manufacturing processes. Traditionally, biodiesel is synthesized via transesterification, as exemplified in FIG. 1. Transesterification, in relation to biodiesel, involves providing a triglyceride molecule or a complex fatty acid, neutralizing the free fatty acids, removing the glycerin, and creating an alcohol ester. This is accomplished by mixing a wood alcohol, e.g., methanol, with sodium hydroxide to make sodium methoxide, which is then mixed into vegetable oil. As the reaction proceeds, contaminant formation of glycerol and possibly some surfactant occurs. The entire mixture then settles, with glycerin on the bottom and methyl esters, or biodiesel, on top (supernatant). Expensive separation of these contaminants is required to produce pure methyl ester or biodiesel.
This typical industry process method includes the use of catalytic reactions with high temperature and pressure. Production challenges include issues of improving the decontamination processes for regenerating the catalysis, reducing dependency on homogenous catalysis that produce unwanted species during the reaction, developing continuous, large volume processes to help reduce costs, reducing environmental impact of decontamination processes, constructing better heterogeneous catalysis without dependency on rare earth materials, constructing a catalysis to work more efficiently with heavier crude oils, improving pharmaceutical process purity with better catalytic reactions, lower temperature and pressure requirements of catalytic reactions, improving surface pour area of catalysis to accept larger molecules, reducing contamination reactions inside the catalysis during production operations, researching to find catalysis that perform reactions in a shorter time period, and improving molecular bonding during catalytic reactions.
After the reaction, the unreacted methanol, or ethanol, and the catalyst must be removed to purify the methyl ester. The expense of this further processing is, at least in part, why conventionally produced biodiesel fuels typically are not cost competitive with petroleum diesel fuel. The production cost of most biodiesel fuels is more than 1.5 times greater than that of petroleum derived diesel. There accordingly is a need in the industry for biodiesel production methods to reduce the use of catalysts and increase useable byproducts, such as hydrogen gas.
Another problem of conventional biodiesel fuel is the cost of refined oil. Crude vegetable oil has considerable free fats that react with the catalyst to form fuel contaminants, such as surfactant and glycerol. Therefore, crude vegetable oil is not a suitable oil source for conventional biodiesel production. These contaminants are costly to remove and formation must be avoided or reduced whenever possible. Conventional biodiesel production requires a homogenous catalysis, which produces unwanted side reactions; these side reactions desirably should be minimized or eliminated from the process.
Reaction time for conventional batch processes of making biodiesel typically ranges from 1 to 8 hours, and separation time for contaminant removal adds another 8 to 16 hours. Researchers have attempted to speed up the slow reaction rate. Examples include the use of non-reactive co-solvents, which converts the two-phase system into a single-phase system. For instance, Canadian Patent Application No. 2,131,654 discloses using simple ethers, such as tetrahydrofuran (THF) and methyltertiarybutylether (MTBE) as co-solvents. Molar ratios of alcohol to triglyceride of at least 4.5:1 are disclosed, with typical ratios being in the range of 6:1 to 8:1. However, this process still produces numerous byproducts which require expensive and time-consuming purification techniques. For these reasons, conventional processes are not economically competitive with petroleum diesel.
Various esterification processes are described in the art. Examples include U.S. Pat. No. 4,164,506 to Kawahara et al. (disclosing steps (a) esterification of free fatty acids in the presence of an acid catalyst, (b) allowing the product mixture to separate into a fat layer and an alcohol layer so as to obtain a refined fat layer, and (c) then subjecting the fat layer to transesterification with a base catalyst); U.S. Pat. No. 4,695,411 to Stern et al. (disclosing a multi-step reaction involving acid transesterification with alcohol in the presence of 1-60% water and separating a resulting glycerol phase, reducing the free acidity of the remaining ester phase and then transesterification in the presence of a base catalyst); U.S. Pat. No. 4,698,186 to Jeromin et al. (disclosing a process for reducing the free acid content of fats and oils by esterification with an alcohol in the presence of an acidic cation exchange resin); U.S. Pat. No. 5,525,126 to Basu et al. (disclosing esterification of mixtures of fats and oils using a calcium acetate/barium acetate catalyst, with undesirable process conditions of 200° C., 500 psi, and a reaction time of three hours); U.S. Pat. No. 5,713,965 to Foglia et al. (disclosing use of lipases to transesterify mixtures of triglycerides and free fatty acids, with reactions requiring 4 to 16 hours to reach conversion rates of 95%); and U.S. Pat. No. 5,520,708 to Johnson et al. (disclosing reaction of triglycerides with methanol in the presence of base to produce fatty acid methyl esters). Various carboxylation processes also are known. Examples include U.S. Pat. No. 5,476,971 to Gupta (disclosing reacting pure glycerol with isobutylene in the presence of an acid catalyst in a two phase reaction to produce mono-, di- and tri-tertiary butyl ethers of glycerol); U.S. Pat. No. 4,013,524 to Tyssee (disclosing method of electrolytic carboxylation and dimerization of olefinic nitrites, esters and amides); and U.S. Pat. No. 4,028,201 to Tyssee (disclosing a procedure for electrolytic monocarboxylation of olefinic nitrites, esters and amides in which the reaction is moderated by protons to direct it toward monocarboxylation); U.S. Pat. No. 5,225,581 to Pintauro (disclosing electrocatalytic process for hydrogenating an unsaturated fatty acid, triglyceride, or mixtures thereof as an oil or fat); U.S. Pat. No. 5,891,203 to Ball et al. (disclosing use of blends of diethanolamine derivatives and biodiesel as an additive for improving lubricity in low sulfur fuels and to fuels and additive concentrates comprising said lubricity additives.)
Examples of other fuel production methods are disclosed in U.S. Pat. No. 6,440,057 to Ergun et al., which discloses a method for producing fatty acid methyl ester, including compounding saturated and unsaturated higher fatty substances from at least one of vegetable and animal with an alkaline solution dissolved in alcohol to form a mixture, and in U.S. Pat. No. 6,248,230 to Min et al., which discloses a method for manufacturing cleaner fuels, in which NPC (Natural Polar Compounds), naturally existing in small quantities within various petrolic hydrocarbon fractions, are removed from the petrolic hydrocarbon. U.S. Pat. No. 6,086,645 to Quiqley discloses low sulfur fuel compositions, which exhibit improved lubricity compared to the low sulfur fuels alone.
In sum, biodiesel made by conventional methods has not been widely accepted because of high levels of contaminants, low BTU values, high NOX upon combustion, or a combination of these factors. Methods are therefore needed to improve the production of biodiesel, for example by increasing efficiency of conversion reactions, improving final product purity and energy values, and/or lowering production costs.
Polymerization
Improved devices and methods are also needed for efficient synthesis of polymers. Many conventional polymerization techniques result in multiple reactions, necessitating tedious separation and/or purification steps. Reducing these purification and separation steps would be invaluable to industries, saving millions of dollars in production cost and reaction time. For example, polyesters are important polymers with multiple uses. Industries would benefit from a more efficient synthesis techniques.
Surfactant
Surfactant production is another chemical industry that could benefit from process enhancements. Surfactants, which are materials that may greatly reduce the surface tension of water when used in very low concentrations, are made of water soluble (hydrophilic) and water insoluble (hydrophobic) components. The hydrophobe may be, for example, the equivalent of an 8- to 18-carbon hydrocarbon, and can for example be aliphatic, aromatic, or a mixture of both. The synthesis of surfactant typically requires some form of catalyst, an oil or fat, and strong base, such as sodium hydroxide. Similar to the syntheses described above, the current methods and devices for the production of surfactant requires several separation and/or purification steps and the use of catalysts, which can be toxic. The sources of hydrophobes are normally natural fats and oils, petroleum fractions, relatively short synthetic polymers, or relatively high molecular weight synthetic alcohols. It would be desirable to provide improved and more efficient processes and devices for surfactant synthesis.
Bioacids
A “bioacid” is an acid composed of esters, which has the formula RCOOH, where R is a long carbon chain. Bioacids are used in a variety of products and processes, including the formation of various polymers that absorb water, settle solids in waste treatment processes, among other applications. Acids used in polymerization processes are usually unsaturated acids (e.g., acrylic, acid, and the like). It would be desirable to provide improved methods of making unsaturated acids from vegetable oil similar to acrylic acid and other bioacids, which would produce fewer unusable byproducts and which would obviate or diminish the need to use organometallic catalysts.
Fatty Acids
A variety of useful and important fatty acids are known. Two essential fatty acids are polyunsaturated fatty acids (PUFAs) that cannot be made in the body: linoleic acid and alpha-linolenic acid (FIGS. 2 and 3). Within the human body, these can be converted to other PUFAs, e.g., arachidonic acid, or omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA).
Linoleic acid is an omega-6 fatty acid. It is biologically inactive before it is catalyzed by the body into other omega-6 fatty acids gamma linoleic acid (GLA), dihomo-gamma linoleic acid (DHGLA) and arachidonic acid (AA). Linoleic acid occurs widely in plant glycerides or fats. Common sources include many vegetable oils such as flax seed, safflower, soybean, peanut, and corn, as well as dairy fats. Linoleic acid is essential in human nutrition and is used also for soaps, animal feeds, paints, drying protective coatings, emulsifying or wetting agents. Other useful fatty acids include oleic acids, as well as palmitic (C15H31COOH) and steric acids (C17H35COOH). Soybean triglycerides contain linoleic and oleic polyunsaturated fats. Fatty acids, such as these, would be useful as or useful in dietary supplements (e.g., fat burners, cholesterol reducers, paints, coatings, emulsifiers, pharmaceuticals, animal feed, soaps, and margarine. It would be desirable to provide new synthetic methods for making fatty acids such as linoleic and oleic polyunsaturated fats.
Ethanol
Ethanol is ubiquitous in industrial processes and consumer products. All beverage ethanol and more than half of industrial ethanol is made by fermentation. Ethanol produced by fermentation typically uses corn as the source of simple sugars. Even though fermentation utilizes mild processing conditions and a renewable resources of raw materials, batch fermentation processes are inefficient, have a slow reaction rate, and yield relatively impure ethanol products.
Other conventional methods for making ethanol use high cost petroleum products, such as alkenes, as the starting material. For example, ethanol is manufactured by reacting ethene with steam, using a catalyst of solid silicon dioxide coated with phosphoric (V) acid. The gas phase reaction is reversible, and must be fractionally reacted in multiple stages at 300° C. at 60 atm to complete the reaction. While these processes are efficient, have a rapid reaction rate, and yield a relatively pure ethanol product, the process requires substantial energy input and uses non-renewable raw material resources (based on crude oil). It would be desirable to provide efficient techniques for producing ethanol and other alcohols from renewable plant-derived raw materials.
Lubricants
Lubricants are widely used, for example, in industrial processing, in transportation equipment, and in various consumer products. Representative examples include hydraulic fluids (tractor, traction motors, tug boats, and the like), transmission fluids (e.g., automobile, truck, tractor, heavy equipment, and the like), bar/chain lubricants, 2-cycle engine oil, crankcase oil, metal cutting, gear oil, greases, coatings (e.g., for metal, wood, or paper), penetrating oils, and inks. Many applications require the lubricant to be thermally and oxidatively stable, such that the lubricant does not degrade over time or during use, particularly in high temperature and high pressure environments. Plant-derived oils, such as soy, cottonseed, and corn oil have different levels of C16 and C18 ester chains with varying levels of unsaturation. The unsaturation levels of most vegetable oils render them insufficiently stable to oxygen and high temperatures. It would be desirable to provide vegetable- or animal-derived oils that exhibit high thermal and oxygen stability for use as or in synthetic oils and lubricants.